Rheostat



Oct. 27, 1936. I TAKANASH] Q 2,058,525

RHEOSTAT Filed April l0,'l935 Patented a. 27, 1936 UNITED STATES PATENTOFFICE BHEOSTAT Masami Takanashi, Tokyo, Japan, assignmof one-half toShungo Furui, Yokohama, Japan Application April 10, 1935, Serial No.15,642 In Japan June 12, 1934 4 Claims. (c1. 201-40) varies linearlywith its length. For this reason, 7

Such means, moreover, do not give very satisfactory results frompractical point of view.

It is accordingly an object of the present invention to obviate theaforesaid disadvantages 20 of the rheostats known heretofore and toprovide a rheostat by means of which the volume of reproduced sounds canbe controlled in a manner proportionate with the movement of controllingmeans.

It is a further object of the'invention to provide a rheostat of thesort just mentioned in a cheap and economical manner.

According to my invention, any desired resistance characteristics, inwhich the effective re- I 30 sistance, instead of linearly with itslength, varies accordingto any desired curve, can be obtained by coatinga portion or whole of each turn of the coil making up a rheostat withmaterial of a higher electric conductivity. In other words,

by making the boundary line formed by the edges of coated portions ofthe turns of coil to extend along a straight line or in accordance witha suitable curve, the effective resistance, or the resist- 40 ance fromone terminal to a contactor brush, can be made to vary parabolically,exponentially or in any predetermined manner with respect to theposition of the brush. By this means, it is made possible to control thevolume of reproduced 1 sound in such a manner that it is substantiallyproportional to the displacement of the contactor brush.

In the accompanying drawing:

Fig. 1 shows an end view, as cover removed, of

50 a rheostat assembly according to my invention.

Fig. 2 shows a central cross sectional view thereof taken at the lineIIII of Fig. 1, with the cover on.

Fig. 3 shows a plan view of a part of the rheo- 55 stat proper, as it isdeveloped in a plane.

' Fig. 4 is a plan view of a modified form of the invention,corresponding to Fig. 3.

Referring to Figs. 1 to 3, and more particularly to Figs. 1 and 2, I isa casing in which are housed a rheostat proper and accessories thereof.The

casing -I has rigidly mounted thereon a sleeve 2,

through the inner bore of which extends a controlling shaft 3. Thesleeve 2 has screw-threads 4 and is adapted with the cooperation of nut5, to serve as a support for mounting the rheostat on a suitable panel.At the inner surface of the cylindrical peripheral portion of the casingI is provided a lining 6 of a suitable insulating material forprotecting the rheostat proper from coming into contact with the wall ofthe casing I. The rheostat proper which is designated by numeral l iscomposed of an insulating inner core 8, resistance wire 9 wound on thecore and terminals IIl connected to the ends of the resistance wire. Therheostat proper is so disposed within the casing I that it is preventedfrom coming into contact with the wall of the casing by means of thelining 6 and the terminals III are caused to project outwardly from theapertures provided at the peripheral wall of the casing and fixed to thecasing in known manner. At the upper edge portion of the rheostat propera sliding contactor I I is provided to contact resiliently with it. Thecontactor I I is formed as an extension of a metallic disc I2 having anarcuate aperture I3 to render the disc resilient. The metallic disc I2is mechanically fixed to the controlling shaft 3, but insulatedelectrically therefrom in known manner. Another terminal I4 is providedon the casing I, as insulated therefrom. This terminal I4 is connectedto a metallic member I5, which is adapted to be in sliding contact withthe disc I2, the terminal I4 being in this manner in electricalconnection with the contactor II. The hub portion of the member I5 iselectrically insulated from the shaft 3 by means of the centralinsulating member I6. The shaft 3 is formed with an annular groove I]for receiving therein a wedge member I8 for preventing thelongitudinal'displacement along the shaft of the assembly including thesleeve 2 and the casing I. The casing I is covered by a cover member I9.The casing I, in cooperation with the cover I9, serves also aselectrostatic shield.

The above mentioned construction is known in itself. The main feature ofinvention will now be described in detail.

Referring to Fig. 3 in particular, which illustrates one realization ofmy invention, the resistance wire 9, such as Manganin, Nichrome andAdvance, is wound on the core of insulator l in such a manner thatadjacent turns do not come into contact with each other. 20 indicatesportions of turns of wire which are coated, electrolytically forexample, with material of a higher electric conductivity, such as copperor silver. In this connection, I have found that the electro lyticalcoating can be advantageously carried out by first coating the wirepreliminarily with nickel and then with copper or silver. Adjacent turnsof the coated portions too are so arranged that they do not come intocontact with each other.

The coating of the turns of the wire is carried out in such a mannerthat the contour line 2| of the edges of coated portions formsubstantially a straight line, when developed, extending diagonally fromone side to the other side of the coil. The coating portions 20,however, can be so prepared as to make the contour line 2| to extendfrom one side to the other side of the coil according to any desiredcurve, for example according to an exponential curve, as shown in Fig.4.

The core of insulator 8 need not necessarily be in plate form, but itmay be made cylindrical or oval in cross-section, or any other suitableform.

In case a rheostat according to the invention is intended to be utilizedfor the purpose of controlling the volume of reproduced sounds in anelectrical phonograph or a radio broadcasting receiver, it can betreated under suitable heat and pressure in a mold with molding powder,such as bakelite or ebonite, so as to form around it an externalprotective covering.

The invention is particularly useful, in its application, as rheostatsfor controlling the volume of sound in electrical phonographs or radiobroadcasting receivers, as has been indicated hereinbefore, although itis also useful in general current regulating purposes, inasmuch as itscharacteristic curve can be varied at will by suitably forming theconductive coating on the rheostatic coiled wiring. Moreover, itsmanufacture is very easy and inexpensive owing to the fact that it canbe produced by a mere coating of ordinary rheostat by a material of goodelectrical conductivity.

What I claim is:

l. A rheostat for controlling the volume of reproduced sound, comprisinga coil of resistance wire, the turns of which are spaced apart out ofcontact with each other, and a coating on a portion or the turns 01'said coil of metal having higher electrical conductivity than said wire,said coating consisting of an electrolytic deposit of nickel on the wireand an electrolytic deposit of copper on the nickel.

2. A rheostat for controlling the volume of reproduced sound, comprisinga coil of resistance wire, the turns of which are spaced apart out ofcontact with each other, and a coating on a portion of the turns of saidcoil of metal having higher electrical conductivity than said wire, saidcoating consisting of an electrolytic deposit of nickel on the wire andan electrolytic deposit of silver on the nickel.

3. A rheostat for controlling the volume of reproduced sound, comprisinga coil of resistance wire, the turns of which are spaced apart out ofcontact with each other, and a coating of metal of higher conductivitythan said wire on said coil, said coating consisting of a deposit .ofnickel on said wire and a deposit ofmetal of higher conductivity thannickel on said nickel deposit, the contour line connecting the boundaryof said coated portion of each turn of wire extending from one end ofthe coil to the other substantially 3 according to an exponential curve.

4. A rheostat for controlling the volume of reproduced sound, comprisinga coil of resistance wire, the turns of which are spaced apart out ofcontact with each other, and a coating of metal of higher conductivitythan said wire on said coil, said coating consisting of a deposit ofnickel on said-wire and a deposit of metal of higher conductlvity thannickel on said nickel deposit, the contour line connecting the boundaryof said coated portion of each turn of wire extending from one end ofthe coil to the other substantially according to a parabolic curve.

MASAMI TAKANASHI.

